Otel 16 (#33)

* Use matrix to test all versions.

* Add support for OTEL 0.16

* Typo.

* Fail on warnings.

* Inject headers when using OTEL 0.16.

* Fix.

.github/workflows/general.yml

@@ -13,9 +13,12 @@ env:
   CARGO_TERM_COLOR: always
 
 jobs:
-  test:
+  test_without_otel:
     name: Test
     runs-on: ubuntu-latest
+    env:
+      # Fail the build if there are warnings
+      RUSTFLAGS: "-D warnings"
     steps:
       - uses: actions/checkout@v2
       - name: Cache dependencies
@@ -35,18 +38,40 @@ jobs:
       - uses: actions-rs/cargo@v1
         with:
           command: test
+
+  test_with_otel:
+    name: Test
+    runs-on: ubuntu-latest
+    env:
+      # Fail the build if there are warnings
+      RUSTFLAGS: "-D warnings"
+    strategy:
+      matrix:
+        otel_version:
+          - opentelemetry_0_13
+          - opentelemetry_0_14
+          - opentelemetry_0_15
+          - opentelemetry_0_16
+    steps:
+      - uses: actions/checkout@v2
+      - name: Cache dependencies
+        id: cache-dependencies
+        uses: actions/cache@v2
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-${{ hashFiles('**/Cargo.lock') }}
+      - uses: actions-rs/toolchain@v1
+        with:
+          profile: minimal
+          toolchain: stable
+          override: true
       - uses: actions-rs/cargo@v1
         with:
           command: test
-          args: --features opentelemetry_0_13
-      - uses: actions-rs/cargo@v1
-        with:
-          command: test
-          args: --features opentelemetry_0_14
-      - uses: actions-rs/cargo@v1
-        with:
-          command: test
-          args: --features opentelemetry_0_15
+          args: --features ${{ matrix.otel_version }}
 
   fmt:
     name: Rustfmt